SHAPE TRACKING OF A DEXTEROUS CONTINUUM MANIPULATOR

• US 20160166341A1
• Filed: 12/15/2015
• Published: 06/16/2016
• Est. Priority Date: 12/15/2014
• Status: Active Grant

• Current Assignee: Johns Hopkins University
• Original Assignee: Johns Hopkins University
• Inventors: Iordachita, Iulian, Liu, Hao, Armand, Mehran, Taylor, Russell H., FARVARDIN, Amirhossein
• Granted Patent: US 10,226,304 B2
• Time in Patent Office: Days
• CPC Class Codes: A61B 2034/102 Modelling of surgical devices, implants or prosthesis
• CPC Class Codes: A61B 2034/2061 using shape-sensors, e.g. fiber shape sensors with Bragg gratings
• CPC Class Codes: A61B 2034/301 for introducing or steering flexible instruments inserted into the body, e.g. catheters or endoscopes
• CPC Class Codes: A61B 2034/306 Wrists with multiple vertebrae
• CPC Class Codes: A61B 34/30 Surgical robots
• CPC Class Codes: A61B 34/35 for telesurgery
• CPC Class Codes: A61B 34/71 Manipulators operated by drive cable mechanisms
• CPC Class Codes: G01B 11/165 by means of a grating deformed by the object
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures

Abstract

A shape sensor system includes a deflection sensor comprising an optical fiber having at least one fiber Bragg grating (FBG) written therein and a substrate, the fiber being attached to the substrate with a selected bias distance from a neutral plane of the deflection sensor. The system further includes an optical source coupled to the fiber to provide input light to be at least partially reflected by the FBG, and an optical detection and processing system arranged to receive at least a portion of the output light and to determine a wavelength shift resulting from a change of an amount of deflection of the deflection sensor. The optical detection and processing system determines a relative amount of deflection of the deflection sensor at the FBG based on the wavelength shift. The selected bias distance is selected based on an expected range of deflection angles to be detected.

Claims

1. A shape sensor system, comprising:

a deflection sensor comprising an optical fiber having at least one fiber Bragg grating (FBG) written therein and a substrate, said optical fiber being attached to said substrate with a selected bias distance from a neutral plane of said deflection sensor;

an optical source optically coupled to said optical fiber to provide input light to be at least partially reflected by said FBG to provide output light; and

an optical detection and processing system arranged to receive at least a portion of said output light and to determine a wavelength shift of at least a portion of said output light resulting from a change of an amount of deflection of said deflection sensor, said optical detection and processing system being further configured to determine a relative amount of deflection of said deflection sensor at said FBG based on said wavelength shift,

wherein said selected bias distance is selected based on an expected range of deflection angles to be detected.

2. A shape sensor system according to claim 1, wherein said substrate is a pair of wires attached to said optical fiber in a triangular configuration as viewed from a cross section thereof.

3. A shape sensor system according to claim 2, wherein said pair of wires are NiTi wires.

4. A shape sensor system according to claim 2, wherein a distance between said pair of wires in said triangular configuration is selected to obtain said selected bias distance.

5. A shape sensor system according to claim 1, wherein said optical fiber has a plurality of fiber Bragg gratings (FBGs) written therein,

wherein said optical source provides light with a plurality of distinguishable wavelength regions to simultaneously address said plurality of FBGs, and

wherein said optical detection and processing system is further configured to determine a plurality of wavelength shifts resulting from a plurality of changes of amounts of deflection of said deflection sensor, said optical detection and processing system being further configured to determine a plurality of relative amounts of deflection of said deflection sensor at said plurality of FBGs based on said plurality of wavelength shifts.

6. A flexible device, comprising:

a flexible elongated portion of said flexible device having a first end and a second end;

a shape sensor system comprising;

a deflection sensor comprising an optical fiber having at least one fiber Bragg grating (FBG) written therein and a substrate, said optical fiber being attached to said substrate with a selected bias distance from a neutral plane of said deflection sensor;

an optical source optically coupled to said optical fiber to provide input light to be at least partially reflected by said FBG to provide output light; and

an optical detection and processing system arranged to receive at least a portion of said output light and to determine a wavelength shift of at least a portion of said output light resulting from a change of an amount of deflection of said deflection sensor, said optical detection and processing system being further configured to determine a relative amount of deflection of said deflection sensor at said FBG based on said wavelength shift,

wherein said selected bias distance is selected based on an expected range of deflection angles to be detected, and

wherein said deflection sensor of said shape sensor system is slidably connected to said flexible elongated portion of said flexible device extending from said first end to said second end.

7. A flexible device according to claim 6, wherein said shape sensor system further comprises a plurality of deflection sensors slidably connected to said flexible elongated portion of said flexible device extending from said first end to said second end.

8. A flexible device according to claim 6, wherein said flexible device is a dexterous continuum manipulator.

9. A deflection sensor, comprising:

a substrate; and

an optical fiber attached to said substrate to have a selected bias distance from a neutral plane of said deflection sensor,

wherein said optical fiber has at least one fiber Bragg grating (FBG) written therein.

10. A deflection sensor according to claim 9, wherein said optical fiber comprises a plurality of fiber Bragg gratings (FBGs) written therein.

11. A deflection sensor according to claim 9, wherein said substrate is a pair of wires.

12. A deflection sensor according to claim 11, wherein said pair of wires are NiTi wires.

13. A dexterous continuum manipulator (DCM) system comprising:

a DCM having a distal end and a proximal end;

a signal processor configured to be in communication with said DCM; and

a display device configured to be in communication with said signal processor,

said DCM comprising;

a first shape sensor attached at said distal end of said DCM and extending through a first lumen along a first side of said DCM to be slidable within said first lumen and at said proximal end of said DCM, and

a second shape sensor attached at said distal end of said DCM and extending through a second lumen along a second side of said DCM to be slidable within said second lumen and at said proximal end of said DCM, and

wherein said signal processor is configured to;

calculate a shape curve of each of said first and second shape sensors starting at said distal end of said DCM;

offset each of said shape curves to a point on a centerline of said DCM;

extrapolate at least one of said shape curves to obtain shape curves of equal length;

calculate a centerline between said shape curves of equal length;

extrapolate said centerline to a predetermine length of said DCM;

determine a tangential direction of a proximal point of said centerline and assign an orthogonal coordinate system at said proximal point;

form a transformation matrix between said distal point and said proximal point of said centerline;

transform said centerline in a space using said transformation matrix; and

offset said centerline in each of at least two opposing directions substantially orthogonal to said centerline by a predetermined amount to establish one of a two dimensional or three dimensional calculated outline of said DCM.

14. The system of claim 13, wherein said DCM is bendable in a plane and said first and second shape sensors are in said plane to provide two-dimensional shape sensing.

15. The system of claim 13, wherein each of said first and second shape sensors comprises an optical fiber with a plurality of fiber Bragg gratings written therein, each said optical fiber being offset from a neutral plane of the corresponding shape sensor

16. The system of claim 13, wherein each of said first and second shape sensors comprises a strain gage.

17. The system of claim 15, wherein said calculating said shape curve of each of said first and second shape sensors is based on:

a linear relationship between curvature and arc length

κ

=a·

s+b

tangent angle of a point with respect to an X axis obtained from

θ

(s)=∫

₀^sκ

(s)ds+θ

₀

and coordinates for a series of discrete points obtained from

18. A method of determining a shape of a dexterous continuum manipulator (DCM) based on a plurality of shape sensors, said DCM having a distal end and a proximal end and comprising:

a first shape sensor attached at said distal end of said DCM and extending through a first lumen along a first side of said DCM to be slidable within said first lumen and at said proximal end of said DCM;

a second shape sensor attached at said distal end of said DCM and extending through a second lumen along a second side of said DCM to be slidable within said second lumen and at said proximal end of said DCM;

said method comprising;

calculating a shape curve of each of said first and second shape sensors starting at said distal end of said DCM;

offsetting each of said shape curves to a point on a centerline of said DCM;

extrapolating at least one of said shape curves to obtain shape curves of equal length;

calculating a centerline between said shape curves of equal length;

extrapolating said centerline to a predetermined length of said DCM;

determining a tangential direction of a proximal point of said centerline and assigning an orthogonal coordinate system at said proximal point;

forming a transformation matrix between said distal point and said proximal point of said centerline;

transforming said centerline in a space using said transformation matrix; and

offsetting said centerline in each of at least two opposing directions substantially orthogonal to said centerline by a predetermined amount to establish one of a two dimensional or three dimensional calculated outline of said DCM.

19. The method of claim 18, wherein said DCM is bendable in a plane and said first and second shape sensors are in said plane to provide two-dimensional shape sensing.

20. The method of claim 18, wherein each of said first and second shape sensors comprises an optical fiber with a plurality of fiber Bragg gratings written therein, each said optical fiber being offset from a neutral plane of the corresponding shape sensor, and

wherein said calculating said shape curve of each of said first and second shape sensors is based on:

a linear relationship between curvature and arc length

κ

=a·

s+b

tangent angle of a point with respect to an X axis obtained from

θ

(s)=∫

₀^sκ

(s)ds+θ

₀

and coordinates for a series of discrete points obtained from